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Wyszukujesz frazę "benthic foraminifera" wg kryterium: Temat


Wyświetlanie 1-3 z 3
Tytuł:
Seasonal variations, environmental parameters, and standing crop assessment of benthic foraminifera in eastern Bahrain, Arabian Gulf
Autorzy:
Arslan, M.
Kaminski, M. A.
Tawabini, B. S.
Ilyas, M.
Babalola, L. O.
Frontalini, F.
Powiązania:
https://bibliotekanauki.pl/articles/2060170.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Arabian/Persian Gulf
benthic foraminifera
standing crop
eastern Bahrain
Opis:
Living benthic foraminifera in a relatively unpolluted site offshore Bahrain in the Arabian Gulf, were studied to determine the seasonal variability of their populations, as well as environmental parameters that may affect their distribution. The maximum foraminiferal density was observed during winter with the assemblages primarily dominated by rotaliids and secondarily by miliolids. The high population is attributed to an increased number of juveniles. A relationship between sediment grain size and the foraminiferal density reveals that juveniles were most abundant on coarse-grained sandy substrate and less abundant on fine-grained substrates. In spring, the foraminiferal density decreased, and the lowest values were observed during summer. The population increased again in autumn with highest juvenile/adult ratios. Moreover, results of relative abundance and species consistency show that Ammonia and Glabratellina are consistent from the shallowest to the deepest station, whereas miliolids occurred only at deeper stations. The numbers of peneroplidae and Elphidium also increased along the depth transect. Environmental characterization reveals that although the site is subject to eutrophication caused by nitrates and sulfates, pollution caused by hydrocarbons and heavy metals is not significant. The assessment of 63 heavy metals showed that none of the metals had concentrations that exceed internationally accepted norms [the devised level of Effect Range-Low], but with high concentration of strontium. The lack of a significant environmental effect of heavy metals is confirmed by the Foraminiferal Abnormality Index of <2%. Likewise, no hydrocarbon contamination was detected in the water or sediment samples. We conclude that the site in Bahrain is not yet adversely affected by human development, and therefore can provide baseline information for future comparison and assessment of foraminiferal assemblages in contaminated zones of the Arabian Gulf.
Źródło:
Geological Quarterly; 2016, 60, 1; 26--37
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The earliest Badenian Planostegina bloom deposit : reflection of an unusual environment in the westernmost Carpathian Foredeep (Czech Republic)
Autorzy:
Kopecká, J.
Holcová, K.
Nehyba, S.
Hladilová, Š.
Brzobohatý, R.
Bitner, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/2059359.pdf
Data publikacji:
2018
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Middle Miocene
Central Paratethys
siliciclastic sedimentation
carbonate sedimentation
large benthic foraminifera
palaeoecology
Opis:
The Miocene sedimentation history of the Brus denudation relict (the western part of the Carpathian Foredeep, Czech Republic) has been inferred from 20 m of silt/siltstones, sand/sandstones and limestones penetrated by the Brus-1 borehole. Detailed multiproxy lithofacies and biofacies analyses have allowed facies and palaeoenvironment interpretations. The presence of molluscs, brachiopods and fish fauna, as well as large benthic and epiphytic foraminifera indicates a generally shallow, subtropical, marine environment. Despite the scarcity of biostratigraphical markers, the section can be correlated with the lowermost Badenian (~15-16 Ma). In the siltstones in the lower part of the borehole, there are abundant low-salinity foraminifera, which may indicate increased rainfall. Linked to this is the nutrient enrichment of the sea bottom water inferred from the presence of the high-nutrient taxa accompanied by abundant calcareous nannoplankton eutrophic taxa such as Coccolithus pelagicus and eutrophic planktonic foraminifera of the Globigerina bulloides/praebulloides group. The main Planostegina bloom was recorded in a sandstone in the interval 12.5-7 m, and was not influenced by a shift from high-organic content Valvulineria assemblage of small foraminifera to an epiphytic one. The boundary between siliciclastic and carbonate sedimentation (-7.5 m) shows a drop in K and Th concentrations, and in the Th/U ratio, but a rise in the Th/K ratio. This change in radioactive element content may generally indicate a significant decrease in terrestrial sediment input which is further supported by the onset of limestone deposition. Reversal of the deposition regime and a decrease of clastic input into the basin may be related to the changing of the precipitation regime, probably triggered by orbitally-forced cyclicity.
Źródło:
Geological Quarterly; 2018, 62, 1; 18--37
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calibration of the Benthic Foraminiferal Oxygen Index in the Marmara Sea
Autorzy:
Kamiński, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/2060479.pdf
Data publikacji:
2012
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
foraminifera
oxygen
ecology
Benthic Foraminiferal Oxygen Index (BFOI)
BFOI
Marmara Sea
Opis:
Benthic foraminifera (total assemblages) were studied from 30 sea-floor samples collected along a bathymetric transect on the southern shelf of the Marmara Sea from depths of 15–350 m. At each station, Kaiho’s Benthic Foraminiferal Oxygen Index (BFOI) was calculated based on species abundances using the methods outlined by Kaiho (1994). The calculated BFOI values were converted to analogue oxygen values, and calibrated to the dissolved oxygen values measured 1 m above the sea floor at each station. In the surface waters and central part of the Marmara Shelf transect, the BFOI values reproduce the measured dissolved oxygen values with a remarkable degree of accuracy. Beneath the pycnocline at depths of 30 to 75 m, the BFOI underestimated the measured oxygen values. This discrepancy is attributed to seasonally higher summer oxygen values within the chlorophyll maximum, corresponding to the position of the Mediterranean Inflow Water (MIW) present during summer. In the deeper part of the transect (below 140 m), BFOI values overestimated the measured oxygen values. This discrepancy is attributed to the presence of denser MIW that cascades down the submarine canyon beneath the Marmara ship channel during winter, ventilating the deep Marmara Sea. The BFOI accurately points out the seasonal differences in the position and depth of the MIW in the southwestern Marmara Sea. The BFOI likely reflects the longer-term oxygen values averaged over the span of many years.
Źródło:
Geological Quarterly; 2012, 56, 4; 757--764
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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